The present invention relates to a vehicle seat of a car, a train, and so on.
In recent year, a vehicle seat using a net member which has a three-dimensional structure, exhibits a high cushioning property even with a thin type compared to a pad member such as polyurethane and the like, and has a plenty of pores to be excellent in air permeability, has been known. The net member is made to have a truss structure (three-dimensional structure) by connecting a front layer and a back layer with a plenty of piles so as to be an elastic structure difficult to settle, and, therefore, is excellent in permeability, body pressure dispersing property, impact absorption characteristics, and so on.
Incidentally, in a vehicle seat, not limited to the case when a net member having a three-dimensional structure is used as the vehicle seat, a sheet-shaped supporting member such as a so-called Pullmaflex and the like which is supported by frame members through metal springs is usally provided under the seat cushion to support an outer layer member elastically and to improve vibration absorption characteristics. Since a net member having a three-dimensional structure exhibits a high cushioning property, excellent impact absorption characteristics and the like, as described above, a net member having a thickness thinner than that of a pad member made of polyurethane and the like can be used for a vehicle seat. However, since the metal springs to support the sheet-shaped supporting member are disposed under the seat cushion, a feeling of something foreign created by the metal springs is apt to be felt. Especially in the vicinity of a greater trochanter where a large load is added, the feeling of something foreign is easily transmitted. This is not limited to a net member having a three-dimensional structure, the same tendency is seen when a relatively thin polyurethane material is used for the outer layer member. Therefore, reduction of such a feeling of something foreign created by metal springs has been hitherto required.
Metal springs which support the sheet-shaped supporting member are arranged in a manner that a plurality of the metal springs per each side of the sheet-shaped supporting member are disposed between each side portion of the sheet-shaped supporting member and each frame member substantially facing thereto at appropriate intervals from the vicinity of the front end to the vicinity of the rear end of the sheet-shaped supporting member. The metal springs are disposed in such a manner that when a load is added by seating of a human body, usually all of these metal springs serve as to enforce each side portion of the sheet-shaped supporting member and each frame member substantially opposing thereto in directions to pull each other, thereby the vibration absorption function is performed by all metal springs.
However, with such a construction, the number of the metal springs serving functionally is the same, regardless of the magnitude of body weight (added load) of the seated person. Accordingly, when the body weight of the seated person varies, the natural frequency of the sheet-shaped supporting member supported by the metal springs is also varied, and a desired vibration characteristic can not be exhibited depending on a body weight of the seated person, which results in dependency on the added load.
The outer layer member using a net member having a three-dimensional structure is usually supported in such that most portions of the peripheral edge thereof are wound around respective frame members constituting a seat frame, which results in a tensile structure in which the outer layer member is put up in a high percentage elongation (for instance, in a range of 10 to 20%) on the seat frame, and there is a room for improvement in view of vibration absorption characteristics at the point more than the resonance point. In order to improve this point, the net member having a three-dimensional structure has to be put up in a low percentage elongation. However, in such a case, there arises a disadvantage that the riding comfort of the car is spoiled due to large sinking-in of the body when seated.
Furthermore, when the seats having different outside design are produced by using plural sorts of outer layer member which are different in shape, material, sew line, or the like, it is normally accompanied by a considerable degree of improvement such as modification of the frame shape and the like to prevent the riding comfort of the car and the like from being greatly spoiled due to the modification of the outside design. However, flexibility in the outside design comes to be low under such a circumstance, therefore it is required to achieve the same riding comfort of the car, and the same vibration characteristic without accompanying improvement in the shape of the frame and the like, even when any sort of outer layer member is used.
The present invention is carried out in view of the above-described circumstances, and its object is to provide a vehicle seat which reduces the feeling of something foreign created by metal springs supporting a sheet-shaped supporting member, and lowers the dependency of vibration characteristic exhibited by the sheet-shaped supporting member supported by the metal springs on an added load. The further object of the present invention is to provide a vehicle seat which improves the riding comfort of the car by restraining sinking-in of the body when seating and has a large flexibility in selecting an outside design.
In accordance with one aspect of the present invention, a vehicle seat is provided to achieve the objects described above. The vehicle seat comprises a sheet-shaped supporting member connectedly supported under an outer layer member constituting a seat cushion by appropriate frame members disposed apart from each other at a distance in the width direction at each side portion of the sheet-shaped supporting member through a plurality of metal springs per each side portion, and the sheet-shaped supporting member supporting the seat cushion and giving the restoring force, wherein the metal spring provided on the position to support the vicinity of the greater trochanter of the seated person in the plurality of the metal springs described above, is provided in a manner that the engagement portion with the frame member is positioned lower than that of the engagement portion with the sheet-shaped supporting member when no load is applied, and within a range of a predetermined added load, the metal spring does not work functionally with each other because respective engagement portions take their positional relationship to be substantially horizontal in a static seating state, while the metal spring works functionally when the added load exceeds the above-described range.
In a preferred embodiment of the present invention, a belt-like member is hung over between the above-described sheet-shaped supporting member and any of the frame members to restrain the reaction force after deformation of the metal spring.
In a preferred embodiment of the present invention, the outer layer member is a net member having a three-dimensional structure in which a front layer and a back layer are connected with a large number of piles.
In a preferred embodiment of the present invention, the outer layer member comprises an inner net which is put up with the frame members to control the sinking-in amount of the body of seated person when seating, and an outer net which covers at least a portion of the inner net, and is put up with the frame members at a percentage elongation of less than 5% when the design standard load is given, and wherein at least the inner net is formed of a net member having a three-dimensional structure in which the front layer and the back layer are connected with a large number of piles.